variance

(va^r' E uns) n.

1. a difference from the usual or expected.

2. Statistics. a measure of the dispersion of a probability distribution, the mean of the square of the difference from the mean.

3. Quality.a. the tendency of the results of a process to vary. b. the failure of a product to meet a particular specification. c. the difference between the actual and acceptable values of a measure. d. the relative frequency of failure in a process.